1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device such as a MOS FET, and especially to a method for manufacturing a semiconductor device including a step of forming an aluminum-containing thin film so as to fill a minute contact hole formed on a semiconductor substrate such as a silicon substrate.
2. Description of Related Art
In the process of manufacturing a semiconductor device, an electrode thin film of aluminum is formed so as to fill therewith a hole-shaped or trench-shaped minute contact hole formed in a semiconductor substrate. Such an electrode thin film functions as a deriving electrode of a device (for example, transistor) formed on the silicon substrate.
Such a thin film has been heretofore formed by supplying aluminum atoms on a silicon substrate using a sputtering method and forming an aluminum thin film so as to fill a contact hole therewith. In some cases, in the step of forming the aluminum thin film, the silicon substrate has been heated so that the contact hole can be easily filled with the aluminum thin film.
However, in keeping with wiring patterns recently becoming minute, the width and the diameter of a contact hole have become smaller (for example, not more than 0.6 μm). On the other hand, the depth of a contact hole has not changed even if wiring patterns have become minute. Therefore, the ratio of the depth of a contact hole to the width or the diameter of the contact hole (aspect ratio) becomes large (for example, not less than 1).
An aluminum thin film capable of suitably filling such a contact hole having a small width or diameter and a large aspect ratio cannot be formed by the abovementioned conventional method. In concrete, there is a problem that a void (air gap) is formed in a portion of an aluminum thin film corresponding to the contact hole. It occurs because, by using sputtering method, the aluminum thin film grows to close the opening of the contact hole before the inner space of the contact hole having a small width or diameter and a large aspect ratio is completely filled with aluminum atoms.
Further, there is another problem that in the step of forming an aluminum thin film or the following steps, aluminum atoms diffuse in diffusion regions or the like on the silicon substrate (aluminum spike) and thereby the p-n junction of a device is destructed.